The first type of latency is player startup
time. At the request of numerous companies
in the industry, I’ve had the chance to perform
extensive tests around this type of latency,
measuring the time difference between a user
request to start a stream and the player’s actual response time.
It’s become a more rigorous and scientific
endeavor in recent years, as time-to-start average rates have dropped from multiple seconds
to less than 1 second. Gone are the days of the
stopwatch—they’re replaced now by reams of
data from logging capture tools. The methodology we employ is to run a series of tests, using our impartial test bed with standardized
content, and then average out the results for
each tested player.
These days, industry averages range in the
900– 1,200 millisecond (ms) range from request
to playback-ready state, but some customized
apps are showing averages down around the
500–650 ms range. These time-to-play tests,
which occur in two controlled environments
using two types of internet service provider
to filter out any single-location anomalies,
only tell half the story, though.
The other latency issue is what occurs both
before and after the user clicks on a link to request a live stream. This latency could be referred to as a lag time, meaning the time the
stream itself lags behind the actual event or
Maxim Erstein, an engineer at Unreal Streaming Technologies, offers a good reason why we
need to differentiate between the two types of
WHAT IS LATENCY? In a word, it means delay. Why is latency important? That’s a much longer—and, for streaming, a much more costly—answer. Because, when it comes to
streaming, latency sucks.
To put latency in the context of streaming media, let’s first consider
which of two latencies we are referring to. That’s a question that
needs to be asked, whether you’re a live content producer looking
to hire a streaming company to acquire a broadcast feed, or you’re
planning to do it yourself.
Erstein says that today
HLS and MPEG-DASH
can help reduce
latency and increase
startup speeds, but
only if their segments
are large and already
reside on the server.